This invention relates to the art of onboard tire inflating and deflating systems for vehicles and, more particularly, to a wheel and axle assembly providing an improved air flow path for the flow of air to and from a vehicle tire across fixed and rotating parts of the wheel and axle assembly.
It is of course well known to provide a vehicle with an onboard system and apparatus to enable the vehicle operator to inflate, deflate and/or check the pressure of the vehicle tires with the vehicle at rest or in motion. Such systems and apparatus include a source of air under pressure carried on the vehicle, appropriate valving and controls for the flow of air to and from the vehicle tires, and sealing arrangements between fixed and rotating components of the wheel and axle assemblies of the vehicle to provide for the delivery of air under pressure to or from the vehicle tires without leakage of air to atmosphere between the sealed surfaces of the fixed and rotating parts.
The parts of each wheel and axle assembly for which such sealing arrangements are required include the fixed axle or axle housing of the vehicle and the rotatable hub assembly which carries the corresponding vehicle tire and is mounted on the axle housing for rotation about the axis thereof by means of a pair of axially spaced apart roller bearing units. In addition to sealing the juncture between the axle and hub components of the vehicle wheel assembly, it is of course necessary to provide a flow path for air between the onboard system and the sealed area and between the sealed area and the vehicle tire. It will be appreciated that these portions of the air flow path are respectively associated with the fixed axle and rotatable hub components of the wheel and axle assembly.
While serving the intended function, arrangements heretofore devised to provide a sealed air flow path between the onboard air supply and the tires of a vehicle have been structurally complex and expensive, and have required special designs or major modifications of otherwise standard vehicle axle, hub and/or bearing components. Such designs and modifications often result in component parts which are limited in use to a given wheel and axle assembly design for a given onboard tire inflating and deflating system. Furthermore, such special modifications or designs, in addition to being expensive, can effect the structural integrity of component parts of a wheel and axle assembly, can void manufacturer's warranties with regard to such component parts if the modifications take place subsequent to manufacture, and do not lend to the efficient and economical retrofitting of a vehicle to provide the latter with an onboard tire inflating and deflating system. More particularly with regard to such disadvantages, the air flow path arrangements heretofore provided have included air flow passageways bored through fixed axle components to deliver air to an area interiorly of the hub and at which point the hub and axle are sealed and the hub provided with a passageway leading from the sealed area to the corresponding vehicle tire. Such arrangements are shown for example in U.S. Pat. Nos. 2,976,906 to Kamm et al; 3,362,452 to Harnish; 3,705,614 to Juttner et al.; and, 4,498,709 to Wells et al. The provision of an air flow bore through the fixed axle component as shown in the latter patents requires a special axle component for a vehicle having an onboard tire inflating and deflating system. Accordingly, a manufacturer providing vehicles both with and without onboard inflating and deflating systems cannot have a standard axle component for both vehicle types. Furthermore, it is time consuming, expensive and perhaps undesirable to retrofit a vehicle to provide an onboard tire inflating and deflating system in accordance with such prior art. In this respect, replacing the existing vehicle axle component is time consuming and expensive and it is both time consuming and extremely difficult to provide the required bore or bores in an existing axle and/or hub components. Moreover, such boring of these parts could well void the manufacturer's warranty with regard thereto.
Other air flow path arrangements heretofore contemplated include those shown in my U.S. Pat. No. 4,705,090 and in my co-pending patent application Ser. No. 286,041 filed Dec. 19, 1988 entitled "Vehicle Wheel Seal Assembly", issued Jan. 9, 1990 as U.S. Pat. No. 4,892,128, the disclosures of which patent and application are incorporated herein by reference. In both my patent and application, axially engageable seal members on the fixed axle and rotating hub components of a wheel and axle assembly communicate the onboard system with the vehicle through axially extending passageways bored in the hub component. While limited to the hub component and parts attached thereto, such boring nonetheless is a special operation in connection with providing original vehicle equipment having an onboard tire inflating and deflating system and, just as importantly and as with the other prior art arrangements, does not lend to efficient or economic retrofitting of a vehicle to provide the latter with such a system. Yet another air flow arrangement heretofore contemplated is shown in U.S. Pat. No. 4,730,656 to Goodell et al. wherein the air flow path between the onboard system and vehicle tire includes a fitting attached to and a bore through the inner race of one of the wheel bearing units. The air path further includes an air chamber between the wheel bearings and which is defined in part by seals mounted on the outer races of the two bearing units and engaging extensions on the inner races of the two bearing units, whereby it will be appreciated that this arrangement requires major modifications of standard bearing designs and special seal units in connection therewith which are not only expensive but limited in use. Furthermore, the bore through the inner race is subject to stress during vehicle operation which can cause bearing failure and, in any event, is likely to shorten the fatigue life of the bearing.